Within the framework of the present invention, said system comprises a plurality of controlling units, preferably of the EEC (“Electronic Control Computer”) type, being respectively associated to the engines of the aircraft, in particular a transport airplane. Each one of such controlling units comprises more specifically means for determining a engine controlling parameter.
As the thrust of a engine cannot be directly known, it is known that each engine manufacturer selects a particular parameter being representative of the thrust of the engine, whatever the operating conditions thereof. Such a engine controlling parameter is generally a complex parameter determined from different data. It could more specifically be an engine pressure ratio of the EPR (“Engine Pressure Ratio”) type representing a ratio between the pressure at the inlet and that at the outlet of the engine. Such an engine controlling parameter, with respect to which the performance of the engine is optimized, is used during the normal operation of the engine in a so-called “main controlling mode” controlling mode.
However, it can happen that a controlling unit is not able to determine said controlling parameter for the engine it is monitoring, for example when one of the data to be used for the determination thereof is not available or is erroneous. Thus, it is generally provided for that each controlling unit is able to determine an auxiliary controlling parameter, for example, the speed N1 of the low pressure compressor of the engine, being associated to a so-called “alternative controlling mode” controlling mode. Consequently, when the engine controlling parameter being associated to the main controlling mode is no longer available on a controlling unit, the latter is automatically brought in an alternative controlling mode, for which it provides said auxiliary engine controlling parameter. However, the performance of the engine is not optimized with respect to such an auxiliary engine controlling parameter so that, in such an alternative controlling mode, the engine is less performing than in the main controlling mode, for some flight conditions.
It is known that generally the engine controlling parameter actually used for by the controlling unit is displayed on a usual system for displaying engine parameters in the cockpit of the aircraft.
Thus, more particularly for maintaining some consistency between information relating to engines, being presented to the crew, it is necessary that the different controlling units use the same engine controlling parameter. This is why, when the main controlling parameter of an engine of the aircraft is lost and the corresponding controlling unit is brought in its alternative controlling mode, the pilot is made aware of such a situation. In such a situation, the pilot is requested to manually switch all the other controlling units in their alternative controlling mode, using usual actuating means, in particular a button, being available in the cockpit.
Moreover, if subsequently the breakdown resulting in such a mode switch disappears, the pilot is requested to actuate again such switching means for returning the controlling units to their main controlling mode.
Such a controlling mode switch, intended for obtaining a consistency of the parameters of engine control to be used and displayed, thus requires the pilot's intervention, representing a significant work load. In addition, if the breakdown resulting in a controlling mode switch is irregular, for example, upon a bad contact, it can happen that the pilot must regularly actuate the actuating means for, each time, controlling the appropriate engine controlling mode.